~ a blog about sustainability at the University of St. Thomas

On not seeing the forest for the trees (or the watershed for the lake)

One lesson I try to get across to my students is the importance of thinking about environmental problems from a holistic perspective. Otherwise, focusing only on one part of a problem can inadvertently worsen other problems (some interesting examples described in this article by Emily Bernhardt).

One problem that I think about a lot (as do many other Minnesotans) is the issue of nutrient pollution in lakes. The classic lake management success story is Lake Washington, near the city of Seattle. During the 1940’s and 1950’s, eleven sewage treatment plants were discharging nutrient-rich treated wastewater directly into the lake. The fertilization of the lake resulted in massive blooms of blue-green algae, and led to fish kills. Based on years of data collected by the limnologist Tommy Edmondson at the University of Washington, phosphorus was identified as the culprit, and a series of expensive engineering projects eventually re-routed the wastewater discharge directly into Puget Sound, bypassing the lake. Over the ensuing decades, water quality improved, and the lake is now twice as clear as it was in 1950.

Something about this story has always bothered me, though. Puget Sound has its own problems with nutrient pollution. Shunting pollution further downstream is an awfully narrow definition of success. Every ecosystem is embedded in a larger ecosystem. Sustainability requires considering the whole, not just one of the parts.

I was reminded of the Lake Washington story by an article that my mother-in-law sent me recently, about Jordan Lake, a reservoir in my home state of North Carolina. This reservoir is a popular recreation spot near Raleigh (I used to kayak there) and provides drinking water for more than a quarter of a million people. And, like many lakes near urban areas, it has suffered from nutrient pollution and algal blooms. To address this problem, the state has imposed strict limits on nutrient runoff throughout the lake’s watershed, a policy that some in the business community have argued is costly and ineffective.

The state is now shifting gears and trying a completely different approach by installing 36 solar-powered pumps throughout the reservoir to circulate water. The idea is that by mixing water from different depths, algae will not have enough light to survive, despite the excess nutrients. The proponent of this plan is a former toxicologist for the EPA, who now works for the company that makes these pumps (and is leasing them to the state for $1.4 million for the next two years). As part of this plan, the state will ease regulations on nutrient runoff.

There’s plenty of politics at play here. The GOP controls the state government now, and is happy to loosen environmental regulations that it considers to be expensive and ineffective. State Senator Rick Gunn, who led the rewrite of the environmental program, claims that high nutrients alone are not a problem.

After years of problems with excess nutrients leading to algal blooms, the state is trying a different approach by installing solar-powered pumps to mix the lake water–while easing restrictions on nutrient control. Image: Wikimedia Commons.

These pumps have been deployed in several other lakes around the country, with mixed results. Will they work here? Maybe. I think it’s an interesting experiment. But the part about easing nutrient restrictions–that gets back to the Lake Washington problem. The thing about rivers is that water moves downstream. Even if the pumps work perfectly and prevent algae blooms in Jordan Lake–and that’s a big “if”–these excess nutrients are going to flow into, and out of the reservoir, and on down the Cape Fear River, eventually reaching the coast where they undoubtedly will cause problems.

This is a case of treating the symptoms and ignoring the underlying problem. Sometimes you need to pay attention to both–and that requires looking at the big picture.